The invention relates to a dynamoelectric machine comprising a stator and a rotor, the stator having a winding system arranged in grooves of the stator, and the cooling system having heat pipes.
Dynamoelectric machines are equipped with an air or fluid cooling system in order to remove the losses of heat from lamination stacks of the stator and/or lamination stacks of the rotor as well as from the winding systems. These losses in dynamoelectric machines arise in particular from iron losses and eddy current losses. In order now to further improve the transporting of heat out of a dynamoelectric machine, heat pipes are used in dynamoelectric machines.
For example, the document U.S. Pat. No. 3,801,843 shows a plurality of arrangements of heat pipes in the lamination stack and grooves of a dynamoelectric machine.
Heat pipes consist in principle of a vacuum-tight sealed pipe which is provided on its inside with a capillary structure. An introduced working fluid (water or alcohol) is stored in the capillary structure as saturated steam as a consequence of the prevailing vacuum. The heat is now transported inside the heat pipes by evaporation and condensation. If heat energy is conveyed to a point of the heat pipes (evaporation zone), then the working fluid evaporates with the absorption of the energy. The steam now flows in the direction of the temperature gradient and condenses at the cooler points of the heat pipes with energy being discharged (condensation zone). The condensate returns into the evaporation zone under the capillary force and under gravity.
Heat pipes are manufactured as pipes, and in particular round pipes, but also as rectangular flat heat pipes. Heat pipes are advantageously arranged in such a way that the evaporation zone is arranged beneath the condensation zone. In the opposite situation, i.e. when the evaporation zone is at the top and the condensation zone at the bottom, the internal capillary force must work counter to gravity.
A dynamoelectric machine in which in particular the end windings are cooled by heat pipes is known from the document JP 10174371 A.
In closed dynamoelectric machines with air cooling, the factor that limits efficiency is often the heating of the rotor. Because the type of protection requires a closed construction of the dynamoelectric machine, the heat must be discharged from the rotor to the cooling air via a protective pipe or the like. The losses of heat from the rotor must now be discharged onto the protective pipe by convection, as is the heat from the winding system, and in particular from the end windings. The protective pipe which is integrated on the bearing pipe is cooled from the outside by cooling air. The following disadvantages arise as a result. The temperature difference between the inside of the protective pipe and the cooling air that flows around the protective pipe is relatively great.
The following factors play a role in the heat transfer: the air speed on both sides, inside and outside the protective pipe, the amount of air, the transfer surface area and the thermal conductivity of the material between the two zones.